Molecular Dynamics Simulation of Mechanical Deformation of Ultra-Thin Metal and Ceramic Films

Abstract

ABSTRACTWe present an overview of the molecular dynamics computer simulation method as employed in the study of the mechanical properties of surfaces at the nanometer scale. The embedded atom method is used to model a clean metal surface and the bond-order model is used to model ceramic surfaces. The computer experiment consists of the indentation and scraping of a hard diamond-like tool into and across the surface. Results are presented for the (111) surface of copper and silver and for the (100) surface of silicon. We explicitly demonstrate in our point indentation simulations that nanoscale plasticity in metals takes place by nondislocation mechanisms, a result suggested by recent nanoindentation experiments. We also observe the surface to accommodate nearly the entire volume of the tip and the annealing out of plastic work as the tip is removed. In our orthogonal cutting simulation, we observe an interesting phenomenon: the system dynamically reorients the grain in front of the tool tip to minimize the work performed on the shear plane (i.e. the shear plane becomes an easy slip plane). Silicon transforms into an amorphous state which then flows plastically.